Schlagwort-Archive: bias

Give us our daily bias

When working today about COVID-19 mortality, I was falling back to the survivorship bias that is nice illustrated at Wikipedia and which is just another type of selection bias that I explained in my last talk.

During World War II, the statistician Abraham Wald took survivorship bias into his calculations when considering how to minimize bomber losses to enemy fire.The Statistical Research Group (SRG) at Columbia University, which Wald was a part of, examined the damage done to aircraft that had returned from missions and recommended adding armor to the areas that showed the least damage, based on his reasoning. This contradicted the US military’s conclusions that the most-hit areas of the plane needed additional armor.

Clearly biased: Maternal recall of asthma in the family

I have heard it many times on congresses and there seems now even a meta-analysis of a possible preferential maternal transmission of asthma to children. And of course, there are important biological question behind (imprinting? maternal antibody transfer?) but unfortunately this is nothing else than a spurious effect.
The author’s view is well taken that we did the first modern family study 1992 Clearly biased: Maternal recall of asthma in the family weiterlesen

When controls are no controls

So far in epidemiology case – control studies are defined by an approach where

… the past histories of patients (the cases) suffering from the condition of interest are compared to the past histories of persons (the controls) who do not have the condition of interest, but who otherwise resemble the cases in such particulars as age and sex ….

I usually explain controls as non-cases in the same overall environment When controls are no controls weiterlesen